04 Understanding_users

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					04 Understanding users
   Lectured by Dr. J. Noiwan
          Jantawan.n@psu.ac.th
    http://host.psu.ac.th/~jantawan.n
Once again, Human Info Proc.




                               2
               Memory
 Stage  Theory
 Short-term, working memory
 long-term memory




                               3
                         Stage Theory
   Moving from sensory memory to working memory (WM)
      attention filters stimuli & passes to WM
   Maintenance rehearsal – rote repetition
      not enough to learn information well

   Moving from WM to Long term memory (LTM)
       remember by organizing & relating to already learned items
       Chunking / elaboration
                                                   maintenance
                                                    rehearsal

                Sensory           Working             Long Term
              Image Store         Memory               Memory

                                            chunking /
                decay        decay,         elaboration   decay?
                             displacement
                                                          interference?
                                                                          4
                         Memory
   Working memory (short term)
       Temporary and small capacity (7 ± 2 “chunks”)
         • 6174591765 vs. (617) 459-1765
         • DECIBMGMC vs. DEC IBM GMC
       rapid access (~ 70ms) & decay (~200 ms)
         • pass to LTM after a few seconds of continued storage
   Long-term memory
       huge (if not “unlimited”)
       slower access time (~100 ms) w/ little decay



                                                                  5
                  LTM Forgetting
   Causes for not remembering an item?
       1) never stored: encoding failure
       2) gone from storage: storage failure
       3) can’t get out of storage: retrieval failure
   Interference model of forgetting
       one item reduces ability to retrieve another
       proactive interference
         • earlier learning reduces ability to retrieve later
           info.
       retroactive interference
         • later learning reduces the ability to retrieve
           earlier info.
                                                                6
         Recognition over Recall
   Recall
      info reproduced from memory

      e.g., command name & semantics
   Recognition
      presentation of info provides knowledge that info

       has been seen before
      e.g., command in menu reminds you of semantics

      easier because of cues to retrieval

        • cue is anything related to item or situation where
          learned
        • e.g., giving hints, icons, labels, menu names, etc.
   We want to design UIs that rely on recognition!
                                                                7
               Attention
 Visual attention
 Selective attention
 Divided attention
 Multiple resource Theory




                             8
        Design Question?


How do we design to obtain understanding
  and focus on relevant information and
                relations?




                                           9
             Visual Attention
 Attention = a selectivity of processing,
  concentration effort on a stimulus, or the limited
  resources available to the cognitive system Eysenck
  and Keane (1995) and Ashcraft (1998).

 When attempting to concentrate on one
  stimulus, a person ignores the surrounding
  stimuli or distractions. This process is called as
  filtering or selecting (Ashcraft, 1998).
 However, objects in a visual peripheral system
  can draw human attention (Driver and Baylis,
  1989).
 Selective attention and Divided attention.

                                                   10
   Selective attention and Divided
 Selective attention
                      attention
      an ability when more than one stimulus is
       presented to a person, but the person is required to
       focus on one stimulus and ignore others.
      Example?

   Wolfe (1998) points out several basic features of visual
    stimuli. Such unique features (e.g., color, motion, and
    size) or so-called “singletons” affect searching
    performance.
   Two attributes of objects that can distract visual attention
    the most are motion and then color (Constantine and
    Lockwood,1999).
   Wickens and Hollands (2000), address that large, bright,
    colorful, changing items on a screen can distract
    attention.
                                                              11
  Selective attention and Divided
             attention
 Divided attention is shared by more than
  one stimulus.
 When attention is divided, performance on
  each task could be lessened.
 Example?




                                          12
      The Multiple Resource Theory
    Several tasks can be                                           Stages
 performed simultaneously
   as long as they do not                      Perception        Working              Responding
   compete for the same                                         memory and
                                                                 cognition
         resources.                                                                                Vocal
                                                                Spatial                                     Responses
                                    Visual
3 dimensions of resources                                                                                  Manual
                                                                             Verbal
1.     Stages of resource    Modalities
       processing
                                  Auditory
2.     Types of modalities
       of input and output
3.     Processing codes
                                             Verbal
Two tasks can interfere
each other (better with                   Codes
                                                      Spatial
diff mode) when
• Have same stimulus
modality
•Use the same stages
•Use the same working
                                                                               Example???
memory for info codes                                                                                         13
Animated Banner Graphics and
       Visual Attention


                         Animated
                         banners




                      Right side of screen?




                                      14
        Animated Banner Graphics and
               Visual Attention



Animated banners




Left side of
screen?




                                       15
     Animated Banner Graphics and
            Visual Attention
   An animated graphic = “a sequence of static images
    changing rapidly enough to create the illusion of a
    continuously changing picture (Baecker and Small,1990).”
   Zhang (1999) and Noiwan (2002) explored animated
    graphic effects toward visual attention in on-line
    information seeking.
   In the periphery, moving targets are detected more
    easily than static ones (Ware, 2000).
   Hillstrom and Yantis (1994) conclude that objects
    presented in a loop of appearance and disappearance
    can attract attention.
   Ware et al. (1992) point out that speed of objects also
    affect attention.


                                                               16
        Controlling Visual Attention
Design principles:
 Structure
       Important information in a central location
       Less important information easy to find (maybe not shown)
   Interaction style
       Sound in danger
       Well considered use of reverse video, blink, intensity etc.
       Color as supplement
   Detail
       Create harmony, symmetry and logical groupings
       Maximum 25% of screen is content
       Use a normal upper-left to lower-right corner sequence

                                                                      17
           Conceptual models
a   conceptual model is
    A generic term that describes the various
     ways in which systems are understood by
     different people
      • A user model maintained by the user to
        conceptualize and understand the system
      • a design model maintained by the interaction
        designer of an interactive computer system.




                                                       18
        The design model, the user’s
        model and the system image
              (Norman, 1986)
   The user mental model
       the user model              Design model       User model
       that is formed through
        interacting with it         Designer                User

       and from its system
        image.
   System image
       the way users get to find          Documentation
        out about the design                   System
        model is through the
                                             System image
        interface, its behavior
        and the documentation.

                                                                    19
                  Mental models
   By interacting with an object, a machine, or human in the
    environment, human is able to create a unique internal
    understanding of what human has perceived.
   Based on this internal understanding, human learns how
    to behave and communicate within such an environment.
   Ex. A traffic stop sign is designed with an octagonal
    shape and red color to make its association with caution
    and danger. (other examples?)
   User formations of mental models is one of the most
    important concepts in facilitating the design of effective
    user interfaces. (Why?)


                                                            20
              Mental models
 A user does not create a unified mental model,
 but rather a collection of various modeling
  techniques which can be applied to support
  human performance. (True?)
 Once the obstacle is solved by one particular
  strategy, this strategy will become part of the
  user’s mental models related to that particular
  problems.
 After that, the user may revise this strategy and
  construct modified mental models based on
  his/her problem-solving experience.

                                                      21
              Mental models
 Changes in the user’s mental models are often
  an unconscious process.
 A user’s understanding of one specific interface
  design can be modified constantly when s/he
  contacts new or relevant information.
  (Example?)
 Thus, the construction of user mental models is
  an indefinite, iterative process, which enables
  these models to evolve constantly to facilitate
  different types of interface designs.

                                                     22
              Conceptual models
   Mismatch between
    designer’s & user’s
    conceptual models
    leads to…
       Errors
       Slow
       Frustration
       ...




                                  23

				
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posted:3/30/2013
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